The mechanisms that regulate host immune responses to the parasite most likely play a pivotal role in the outcome of infections with lymph dwelling filarial nematodes. The specific goals of the proposed are: 1. To define the mechanisms of immune suppression most manifest during patent filarial infections, and 2. To identify filarial antigens that elicit suppressive immune reactions. The key features of the approach I propose are: 1. To utilize classic hapten-carrier concepts and methodology to dissect humoral immunity to a human parasite, Brugia malayi, in an inbred rat model, and 2. To identify and isolate filarial antigens with suppressive potential with mono-specific monoclonal antibodies generated by the technique somatic hybridization. The long-term objectives of this study are to provide the basis for a rational approach to immune intervention in a disease where most maninfestations appear to have an immunologic basis and which affects the health and well being of an estimated 300 million human beings worldwide.